The goal of this proposal is to address hypotheses regarding the imaging and therapy of cancer, in particular the targeting of the process of cancer metastasis with 64Cu-labeled peptides that target the avB3 integrin. The process of cancer metastasizing to the bone has been shown to be highly dependent on the presence of integrins, in particular the B3 integrin. Developing a bone imaging agent which specifically targets the avB3 integrin will allow clinicians to discriminately target sites of bone metastasis and would permit them to better determine the efficacy of a patient's treatment and plan additional therapy as needed. The specific aims, in brief, are (1) to develop 64Cu-CB-ligand conjugated peptides which possess enhanced in vivo stability. (2) Use micro PET imaging in conjunction with in vitro analysis to determine the binding affinity of these 64Cu-Cbligand conjugated peptides for the avB3 integrin, and to evaluate the use of the radiopharmaceuticals as PET bone metastasis imaging agents; and (3) to evaluate these 64Cu-CB-ligand conjugated peptides as therapeutic agents for bone metastasis.